This invention relates to a device for measuring and transmitting the combustion radiation in the combustion chamber of combustion engines in which the combustion radiation occuring in the combustion chamber is sensed in the movable part of the combustion engine by optical sensors and is transmitted through optical light guides to the fixed part of the engine.
In research and development work in the area of combustion engines the flame propagation and the flow conditions in the combustion chamber are experimentally determined in order to obtain information on the cooperation of flame propagation, flow movement and engine parameters. For determining the flame propagation, the optical light guide measuring technique is often used, while the flow motion is in most cases determined with the aid of laser Doppler anemometry.
The light signals of the flame, received by optical probes, are transmitted by optical light guides to photomultipliers, converted into digital electrical signals and evaluated as logical signals by means of a computer program. The result is the spacial contour of the flame front in dependence on time. It is necessary to determine the light emission above the cylinder wall as well as through pistons and cylinder head.
Here the problem occurs of arranging optical measuring areas for determining the flame propagation also in the movable part of the engine, which usually is the piston, and to transmit the flame signals to the non-movable part of the engine for transmission and evaluation.
It is known from SAE paper 872060 entitled "An Experimental Study of Combustion and Fluid Flow in Diesel Engines" of Nov. 2, 1987, to perform this transmission by means of optical fibers which transmits the flame signals registered in the piston to the photomultipliers located outside the crank case. The optical fibers extend from the measuring points in the piston through or along the connecting rod and lead from there via a coupling linked to the connecting rod and an oscillating crank to the photomultipliers outside the crank case. The oscillating coupling system is designed such that the optical fibers are not overtaxed by the alternating charge. For this purpose the optical fibers are led via straps or through the joint bolts past the respective joints. With the use of fiberglass rods which have been adapted to the respective geometry of the piston by means of heat treatment, the light signals are transmitted from the piston head to the flexible optical fibers.
Such an arrangement has the advantage of an optically impeccable and relatively reliable transmission of the flame signals, but is by nature expensive to construct and has a limited durability due to the high alternating charge with higher number of revolutions under elevated temperatures. It is also not suitable for operational use in the motor vehicle.
From DE No. 30 23 471 A1 it is known to convert in an electro-optical transmitter the electrical signals into light signals, to transmit these light signals between mutually movable parts and then to reconvert the light signal back to electrical signals in an opto-electrical converter. In this manner it is possible to eliminate the disadvantages caused by friction and wear in slip ring transmission. However, such an arrangement only permits the transmission with parts which are continuously on a common rotation axis, but no transmission with parts that move against each other in a translatory manner or otherwise.
In EP No. 0 229 399 A2 a device for the wireless transmission of signals from a rotating body, particularly from the clamping chuck of drills, is disclosed. Here too, only light signals of the visible or infrared radiation are produced for the transmission of electrical signals. For application to combustion engines it is possible, if at all, only to expect overall statements regarding gas forces and oscillation. More detailed conclusions regarding the course of the combustion and thus the actual combustion process, as well as the type of flame propagation, are not possible.